William Julius Green is an American professional basketball coach and former player who currently is an assistant coach for the Dallas Mavericks of the National Basketball Association (NBA). He played professionally in the NBA with the Philadelphia 76ers, New Orleans Hornets, Atlanta Hawks, Los Angeles Clippers, and Orlando Magic. He was selected in the second round of the 2003 NBA draft by the Seattle SuperSonics and later acquired by the Philadelphia 76ers from Seattle in a draft-night trade for the draft rights to Paccelis Morlende and cash considerations.